-LRB- CNN -RRB- -- Over the past week , I 've been inundated with questions about swine flu , via Facebook , Twitter , CNN blogs and e-mail . So this week I 'm empowering people with information about swine flu : how to protect yourself , what all the numbers mean and why you should n't freak out .

The most recnt advice from the CDC is that non-essential travel to Mexico should be avoided .

1 . Has n't swine flu been around for a while ?

Yes . Swine flu was first identified in 1930 when researchers isolated the virus in a pig . In 1976 , more than 200 soldiers at Fort Dix , New Jersey , got swine flu . From 1976 until 2005 , the U.S. Centers for Disease Control and Prevention received approximately one report every year or two of humans with swine flu . From December 2005 until January 2009 , there were 12 cases of swine flu reported .

2 . The folks who have it now , did they get it from pigs or people ?

It appears that no one in the United States with swine flu had any contact with pigs . Dr. Richard Besser , the acting director of the CDC , said in a news conference Friday that among the first seven cases , no one had contact with pigs . In another press conference Monday , he added that investigators have looked to see whether any of the infected people had contact with pigs , and `` we 're not finding that linkage here . ''

3 . Swine flu is transmitted from animals to humans . Does that happen a lot ?

Yes . More than 200 `` zoonotic diseases '' are transmitted from animals to humans , including illnesses caused by bacteria , viruses and parasites . Rabies and variant Creutzfeldt-Jakob disease -LRB- better known as `` mad cow disease '' -RRB- are two well-known examples .

4 . Should I cancel my trip to Mexico ?

Yes , you should , unless it 's essential . That 's the advice from a recent CDC travel warning . Watch Elizabeth Cohen answer your questions ''

5 . Should I be freaking out ?

A new virus spreading quickly around the world . Young , healthy people struck dead in Mexico . Should we all be panicking ?

`` Absolutely not , '' said Dr. William Schaffner , chairman of the department of preventive medicine at Vanderbilt University School of Medicine . Swine flu , he said , `` is not spreading all that rapidly . Take the St. Francis School in New York . There 's been very little transmission from the schoolchildren to family members , and it certainly has n't spread throughout Queens . '' iReport.com : Share your thoughts , concerns about swine flu

But , Schaffner added , this does n't mean we should n't pay attention to swine flu . `` We should be alert , keep up with the information coming out daily , and take control by being attentive to your hygiene . Wash your hands very , very frequently and avoid people who are coughing and sneezing . ''

6 . How close do you have to be to a sick person to get swine flu ?

`` You can acquire this infection if you 're within the ` breathing zone ' of a sick person , which is about three to six feet , '' Schaffner said . `` And we usually mean being this close to someone in a confined space . We 're not talking about fleeting contact . We 're not talking about walking past someone in the street . You need sustained contact . '' If you think you might have sustained contact with someone who 's ill , read this guidance from the CDC 's Web site .

7 . Yikes ! Every day I 'm that close to countless people -- at work , on the bus , at church , in a movie theater . Could I get swine flu from them ?

Yes .

`` If you 're standing next to someone on a bus , or sitting next to someone or in front of someone in a theater , you could acquire the infection in that fashion , '' Schaffner said . That 's why people with the symptoms of any kind of flu -- fever , diarrhea , body aches , vomiting , etc. -- are urged to stay home and away from groups of people .

8 . Was n't there a vaccine at one time ? Is there one now ?

Yes , a swine flu vaccine was given to 45 million people in 1976 . There is no vaccine now , although researchers are working on one .

The 1976 vaccine would n't be helpful anyway , according to Dr. Anthony Fauci , director of the National Institute for Allergy & Infectious Diseases .

`` That was a completely different virus than the virus we are dealing with right now , completely different in the sense that the genes are different , and it does n't have any relationship , '' said Fauci . `` The designation of each one was called the swine flu , but from a viral standpoint and spreading it is quite , quite different . ''

Here are two scientific articles about the swine flu outbreak and vaccination program in 1976 :

• Reflections on the 1976 Swine Flu Vaccination Program

• Swine Influenza A Outbreak , Fort Dix , New Jersey , 1976

9 . Many young , healthy people have become sick in the United States . Many of the dead in Mexico have been young and healthy . What 's going on ? Usually we think of flu as affecting the very young and the very old .

This sometimes happens with new viruses . For example , in 1918 when a new flu virus emerged , many of those stricken were young and healthy . One theory is that young people , who have strong immune systems , mount a particularly vigorous response to new viruses . But there 's a potential side effect to the response : the body releases dangerous levels of signaling proteins , called cytokines , which can damage the lungs . Scientists believe these `` cytokine storms '' can be fatal .

Here is a scientific article about the proposed mechanism of cytokine storms .

10 . Why are large numbers of people dying in Mexico , but not in other countries ?

This is the big mystery doctors are trying to solve right now . Many infectious disease experts say it 's most likely a matter of numbers : with more illnesses in Mexico , there are also more deaths . Other explanations : that in Mexico people have , in addition to swine flu , other viruses that make for a more deadly combination than swine flu alone . It 's also possible that the virus infecting the rest of the world is a weaker version than the one in Mexico . Among the swine flu mysteries : Why only deaths in Mexico ?

11 . Could this new swine flu virus have been manufactured by bioterrorists ?

That 's the theory on some conspiracy theorists ' Web sites . But experts do n't believe it .

`` If you were a bioterrorist you 'd want to create something that 's a lot more deadly than this , '' said Dr. Gerald Evans , an associate professor of microbiology at Queen 's University in Canada . `` The problem with influenza is that the second you put it into people , it replicates and mutates very quickly . Even if you created the perfect bioweapon , within a few generations of transmissions , it would n't do what you planned for it to do . ''

12 . I get a flu shot every fall . Will that help protect me against swine flu ?

`` The short answer is that the CDC says it 's very unlikely , '' Schaffner said . But he said it might be possible . `` I think it 's a bit of an open question whether repeated flu shots over years would provide a measure of protection . ''

13 . I was in Mexico two weeks ago . Could I have contracted swine flu , and the symptoms just have n't shown up yet ?

No . The incubation period of the swine flu is one to seven days .

`` If you just traveled to Mexico and you 're home and feeling well you should get on with your daily life and not worry about it , '' Evans said .

14 . Can the swine flu virus live on inanimate objects ? If someone with swine flu touches a doorknob , then I touch it , could I get swine flu ?

Flu viruses can live on inanimate surfaces . So theoretically , you could get swine flu from touching a doorknob that was just touched by an infected person . However , that 's pretty unlikely , according to Dr. Arthur Reingold , head of epidemiology in the School of Public Health at the University of California , Berkeley .

`` I personally would not have a major fear of environmental contamination , '' he said . `` Virtually all influenza is transmitted from sneezing and coughing . ''

Schaffner agrees , adding that flu viruses do n't survive in large numbers on surfaces . `` A doorknob is n't a warm , nourishing environment for a virus , '' he said .

15 . What should I do if I develop symptoms of swine flu ?

Call your doctor -- do n't just drive on over , Schaffner advised . `` Follow the instructions of your doctor . He might not want you in the waiting room spreading germs to others , '' he said .

CNN Medical Producer John Bonifield contributed to this report .

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The emergence of the swine flu has raised many questions ; here are some answers

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Swine flu was first identified in 1930 when researchers isolated the virus in a pig

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Why people are dying in Mexico but not in other places is still a mystery

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While the virus can live on surfaces , transmission is unlikely